Dual slit photodetector e.g. phototransistor, for use in e.g. position determination device for determining position in encoder sensor, has outer and inner photo-active surfaces provided with different length-to-width ratios

摘要

The photodetector (1) has outer photo-active surfaces (4, 5) provided with a small length-to-width ratio of 5, and inner photo-active surfaces (2, 3) provided with a large length-to-width ratio of 10. The inner and outer photo-active surfaces are arranged parallel to a common substrate. The outer photo-active surfaces are arranged around the inner photo-active surfaces on the common substrate. An outer movable safety screen is arranged at a large distance to the photodetector. An incident light hits an optical grid element and is diffracted in a wavelength dependent manner.